Elastic sheet materials are commonly incorporated into products (e.g., diapers, training pants, garments, etc.) to improve their ability to better fit the contours of the body. For example, an elastic composite may be formed from an elastic sheet material and one or more nonwoven web facings. The nonwoven web facing may itself be extensible. Alternatively, the nonwoven web facing may be joined to the elastic sheet material while the elastic sheet material is in a stretched condition so that the nonwoven web facing can gather between the locations where it is bonded to the elastic sheet material when it is relaxed. The resulting elastic composite is stretchable to the extent that the nonwoven web facing gathered between the bond locations allows the elastic film to elongate.
Styrenic block copolymers are often employed to form the elastic components of such composites. For example, the styrenic block copolymer may contain a conjugated butadiene block positioned between two styrene blocks (i.e., S-B-S). Styrenic block copolymers containing conjugated butadiene blocks may be cross-linked to improve elastic performance. Suitably, the styrenic block copolymers may be melt extruded to form the elastic sheet materials. However, such polymers may be difficult to process by melt extrusion due to premature cross-linking of the butadiene block during the extrusion process. As such, a need exists for elastic materials that have good melt stability during processing, yet exhibit good elastic performance during use.